1. Field
Example embodiments relate to a plasma processing apparatus.
2. Description of the Related Art
A plasma processing apparatus, for example a plasma processing apparatus that generates plasma using a microwave, may be used to form an insulating film on a semicondoctor wafer and/or etch a film on a semiconductor wafer.
In some plasma processing apparatuses, electric current may be transmitted to an antenna in order to generate a plasma. An antenna may be provided between an upper plate and a lower ring and the lower ring may be pressed by a bolt. The antenna may be a conductor. During operation, when electric current is transmitted to an antenna, the antenna may generate heat due to the resistance of the conductor.
Due to thermal expansion effects, a circular antenna may expand in a radial direction when heated.
However, when a bolt passes through the antenna, the bolt may limit the antenna from being lengthened in the radial direction. Instead, the antenna can swell upward.
The top of the antenna may be supported by the clamping force of the bolt. The thermal expansion of the antenna may exert a force on the antenna.
Over time, heating may deform the antenna. Deformation of the antenna may have negative effects on the plasma process in which the antenna is used and may cause a slot in the antenna to arch.
In order to limit the antenna from heating, a thickness of an upper insulator may be reduced and the temperature of cooling water may be lowered. As a result, plasma generation efficiency may deteriorate and condensation may occur near the upper plate. An additional apparatus to prevent condensation may be required.
Thermal expansion may also oxidize the surface of the antenna. In order to limit oxidation on the antenna surface, the antenna may be plated with gold. However, the gold-plated layer can be detached.